PROJECT SUMMARY/ABSTRACT The mixed methods explanatory-sequential (QUANT?quant) parent study will test a conceptual model of social-structural stressors, protective factors, and drug use and co-occurring negative mental and physical health outcomes among Black men at the intersection of sexual identity and socioeconomic position (SEP). Informed by the intersectionality theoretical framework, the initial design for the parent study provided for three sexual identity categories (i.e., gay, bisexual, and heterosexual) and two SEP positions (i.e., lower, higher) and a sample size of 1,440 (i.e., 240 participants for each of the 6 sampling frames: lower- SEP gay, lower-SEP bisexual, lower-SEP heterosexual, higher-SEP gay, higher-SEP bisexual, higher-SEP heterosexual). The considerable challenges involved in recruiting bisexual men and doing so at two different SEP-categories, was methodologically infeasible given the study's 5-year timeframe and limited resources. Thus a single sexual minority (SM) category composed of gay, bisexual, and other men who have sex with men was created to produce a sampling frame stratified by just two sexual identity positions (i.e., SM and heterosexual). A determination was made that this sampling frame was more methodologically feasible in terms of recruitment because it provided for a sample size of 960 (i.e., 240 participants each of lower-SEP SM, lower-SEP heterosexual, higher-SEP SM, higher-SEP heterosexual). To address the critical gaps that exist about Black bisexual men's health, the goal of the proposed administrative supplement is to increase the number of Black bisexual men participants and establish bisexual men as a distinct SM position for all of the parent study's analyses. To accomplish this goal, an academic-community partnership will be established with BiNet USA, the oldest national bisexual organization in the U.S. The proposed supplement adds new primary inferential and exploratory analyses specific to bisexual men (Aim 1, parent study). It also adds a convergent mixed methods design component in Phase I in which in-depth qualitative interviews will be conducted during the Phase I quantitative analyses with 30 purposively sampled Phase I quantitative bisexual participants. The interviews will facilitate a rich, culturally and contextually-grounded understanding of Black bisexual men's experiences relevant to the parent study's focus, as well as their intersectionality-specific experiences (e.g., binegativity). For Aim 3 of the parent study, Phases II (Focus Groups to Explain the Phase I Quantitative Results) and III (Mixed Methods Syntheses and Assessment of Validity) are unchanged. Bisexual participants will be purposively sampled for the Phase II focus groups. Phase III quantitative and qualitative synthesis analyses will assess the convergence and divergence of results for bisexual participants. This specific focus on bisexual participants represents a paradigmatic shift in sexual minority research. The significance of the proposed research lies in the expected outcome of the future development of multilevel interventions to reduce drug use and promote mental and physical health for Black bisexual men.